1. Field of the Invention
The present invention relates to an apparatus for determining the dimensions of an object. More particularly, it relates to a dimensioning apparatus for determining the minimum size box necessary to enclose an object. Most particularly, the invention is directed to an automatic dimensioning system which accurately determines the dimensions of an object on a moving conveyor for package sorting and handling applications.
2. Description of the Prior Art
In order to reduce costs and increase the volume of packages handled, the shipping industry has pressed automated package handling. This has been accomplished through automated package identification by bar code labeling and automated sortation by scanners identifying the labels and routing the packages. Package sorting is typically done based on the package size. In the shipping industry, shipping fees are directly related to the package size, weight and shipping destination. Determining the correct package size in an efficient manner is therefore especially significant for both throughput and fee calculation.
While some progress has been made to provide automated systems for creating a three dimensional rendering of the package, the known systems are both complex and costly. There are several known systems for obtaining package dimensions. One system, shown in U.S. Pat. No. 5,193,120, utilizes a light source which projects collimated lines of light onto the object to be measured. An imaging system, utilizing a video camera, views the object at an angle with respect to the structured light so that the profile of the object can be visualized. The video signal is processed to calculate the three dimensional rendering of the object based on the lines of light.
Another system, shown in International Publication Number WO 94/27166, uses a laser beam which is reflected in a fan shaped form and directed using mirrors to a flat surface. The laser beam is oscillated at a high frequency where the difference in phase between the originating beam and the reflected light off of the surface of an object yields the height of the object. The system calculates the time it takes for the light beam to travel to and from the object. The system is mounted in a moveable carriage which passes over the object and after a multiplicity of height measurements determines the dimensions of the object.
U.S. Pat. No. 4,758,093 discloses a three-dimensional measurement system which uses a holographic scanning mechanism. Triangulation based upon the projector to camera and relative angles provides the foundation for computing the surface coordinates.
An apparatus which determines an object's height is shown in U.S. Pat. No. 4,929,843. This system utilizes a laser beam which is rastered across a conveyor surface creating a light stripe. A television camera, having a defined field of view, views the object at an angle causing the apparent location of the light stripe to move based on the object height.
Although the known systems can be used to obtain an object's height or to provide a three dimensional rendering, both systems view the object area at an angle, then produce a large analog video signal which must be filtered and processed. In order to increase the efficiency and reduce the cost of a dimensioning system, it is desirable to have a low cost, automated means for providing an accurate, high speed rendering of an article as it is carried on a conveyor. This object can be accomplished by reducing the amount of visual data processed.